Rania SAOUDI defended her PhD on July 17th, 2023.
Place : Université Lyon 1, Marie Curie amphitheâtre-
Jury :
Rapporteurs :
Mme. LEBOUC Afef, Directrice de Recherche, CNRS Grenoble
M. BENABOU Abdelkader, Maitre de conférences, Université de Lille
Examinateurs :
M. DANIEL Laurent, Professeur des Universités, Paris Saclay
M. JOUBERT Charles, Professeur des universités, UCBL 1
Invités:
M. Atef LEKDIM, Ingénieur de recherche, LEM Tech, Lyon
M. Thierry WAECKERLE , Directeur R&D, APERAM, Imphy
M. Alain DEMIER, Ingénieur de recherche, APERAM, Imphy
Encadrement :
M. Laurent MOREL, Maitre de conférences, UCBL 1 Directeur de thèse
Mme. Marie Ange RAULET, Maitre de conférences, UCBL 1 Co-directrice de thèse
Abstract :
In the context of increasing energy efficiency, electrical systems need to be designed in a very compact way in order to reduce their volume and weight, specifically in systems used in transportation (automotive, rail and airplanes). This compactness leads the magnetic materials of the new electrical converters to operate in severe environments (high temperatures and high frequencies).
This thesis focuses on the behavior over time (aging) of FeCuNbSiB nanocrystalline materials dedicated to the design of transformers, inductors and current sensors. Different grades of nanocrystalline materials were provided by our collaborator APERAM Imphy in the form of wound cores. At first, nanocrystalline materials are studied during continuous aging under different temperatures. In aim to monitor aging evolution, several macroscopic magnetic properties are measured at each aging period. In order to explain the aging mechanism, an analysis of the anisotropy energies is conducted, completed by measurements at different scales (local, mesoscopic and microscopic). Thereafter, the magnetic properties of nanocrystalline materials are monitored during their thermal aging under alternating excitation. The latter is applied using electronic circuits designed for fluxgate current sensors provided by LEM. Finally, the impact of magnetic aging of nanocrystals on the evolution of sensor parameters is studied.
Keywords: Nanocrystalline materials; Ferromagnetism; Annealing conditions; Anisotropic energy; Magnetic aging; Magnetic characterizations; Fluxgate current sensors.